1. Field of the Invention
The present invention relates to a hydraulic shoe bolt wrench used to mount and remove shoe bolts by which shoes are secured to a track chain consituting a shoe track of a construction machinery.
2. Prior Art
With the recent larger-size of construction machineries, shoe bolts also have a large diameter and a fastening torque is set to a high level. For example, in the class of 100 ton, the diameter of bolts is set to 36 mm and the fastening torque is set to 310.+-.30 kg f.m. Therefore, the hydraulic wrench as previously disclosed in Japanese Patent Application Laid-Open No. 255333/1985 by the present applicant is not sufficient to meet the requirement.
In order to attain an initial high speed turning work by a single high torque hydraulic motor as disclosed in the aforementioned conventional apparatus, a hydraulic pump for supplying a large capacity of pressure oil and a larger motor for driving the pump are required, and in addition, even if it is rotated at high speeds, instantaneous stop thereof is impossible due to the inertia, and therefore, it is difficult to further rotate it by the inertia force after reaching to a defined torque value to obtain an accurate defined fastening torque.
Further, a hydraulic wrench has been proposed to increase the fastening torque. In this apparatus, a cylindrical ratchet for connection and disconnection is interposed between a wrench socket and a low-speed high torque motor, and it is rotated in the outer periphery of the cylindrical ratchet by a stroke of a hydraulic cylinder to obtain a predetermined fastening torque or an additional fastening.
However, the apparatus is designed so that a cylindrical clutch is rotated by the linear motion of a fixed cylinder, and therefore, a rotation transmission torque is varied by the angle of rotation of the cylindrical ratchet.
Furthermore, normally, in this system, the fastening torque is set by oil pressure to the hydraulic cylinder. Therefore, the torque value of the actually fastened bolt is different from the set value.
Moreover, in this apparatus, the succeeding operation cannot be made unless the hydraulic cylinder is returned to its original position. Therefore, there involves disadvantages that the workability is poor, and that frictional noises of the ratchet occur during the returning stroke of the cylinder.